This application claims the priority of German Patent Application No. 101 40 864.1 filed on Aug. 21, 2001, the disclosure of which is being incorporated herein by reference.
The invention relates to a system for the needle-treatment of a conveyable fiber bat, and more particularly to a system which includes at least one conveying device having a plurality of needles which are pushed into and subsequently withdrawn from the fiber bat.
The fiber bat is subjected to tension during fiber-bat processing when the needles, which are inserted into the fiber bat during the needle-treatment, restrain a continuous conveyance of the fiber bat. This tension can lead to an undesirable stretching of the fiber bat in the conveying direction. U.S. Pat. No. 5,909,883A discloses a system in which the withdrawing roller drive is controlled so that the conveying speed is reduced during the needle intervention to take into account the tension on the fiber bat which increases when the needles penetrate into the material. However, this is tied to a comparably high design and control expenditure. Less complicated means for lowering the tensile stress of the fiber bat during the needle insertion are disclosed in Austrian Patent No. 259,246B1, in which one of the two rollers of a roller pair is designed with diametrically opposite arranged driver cams for the fiber bat. In dependence on the lift frequency of the needle board, the roller is operated such that a frictional connection between conveying rollers and fiber bat exists only if the needles of the needle board release the fiber bat. Such an intermittent conveying drive for the fiber bat represents an advantageous condition for a needle-treatment of the fiber bat with little tension. However, this intermittent conveying effect also requires a uniform thickness of the fiber bat that cannot be ensured in practical operations. Unavoidably thick and thin areas in the fiber bat result in irregularities in the advancement of the fiber bat and thus also in an irregular needle-treatment. Furthermore, thickened areas in the fiber bat can result in damage to the fiber bat surface, caused by the driver cams of one of the conveying rollers impacting on the fiber bat, and can lead to a mechanical overload of these conveying rollers, in particular in the bearing region. Another disadvantage is that a high operating speed is not possible with the known intermittent operation of the needle. According to a prior suggestion, the needles are rigidly arranged on the outside surface of a belt that circulates endlessly around two deflection rollers. In the process, a relative movement occurs between needles and fiber material, which pulls the fiber material out of shape. Specifically, when the needles are pushed in and pulled out of the fiber material at the two deflection locations, relative movements between the needles and the fiber material occur because of the slanted positioning of the needles relative to the fiber material. These movements lead to a stretching in the conveying direction and, in particular, to an irregular structure of the fiber material.
It is an object of the invention to provide a device of the aforementioned type that avoids the above-mentioned disadvantages and, in particular, makes it possible to have a high needle-treatment speed and a uniform structure of the needle-treated fiber bat. The conveying device can form part of a needle-treatment system.
The above and other objects are achieved according to the invention by the provision of a system for performing a needle treatment operation on a conveyable fiber bat, comprising: at least one circulating endless conveying device having an outside constituting a conveying surface for the fiber bat and an inside; a plurality of wire needles positioned for penetrating the conveying surface from the inside toward the outside and back again, and for being pushed into and withdrawn from the fiber bat; and, means for moving the conveying surface, the fiber bat, and the needles at the same speed during the needle-treatment operation.
A high needle-treatment speed and a uniform fiber bat structure are attained with the conveying device according to the invention since the conveying surface or surfaces, the fiber bat, and the needles, during penetration and withdrawal, have the same speed in the conveying direction; moreover, the needles penetrate and are withdrawn from the fiber bat in a direction perpendicular or nearly perpendicular to the fiber bat conveying direction during the needle-treatment operation. A careful and effective needle-treatment of the fiber bat, i.e., the fiber material, thus occurs without any relative speed between the fiber bat and the needles during the conveying operation. The conveying device imparts this careful needle-treatment to a range of fiber bats, including thick fiber bats and fiber bats with short fibers. A high throughput speed can be attained with the conveying device. The extended penetration phase contributes to the high throughput speed. Further advantages of the device are low weight, compact design, and low noise during operation. The design of the device permits a modular construction. The needle treatment can be realized on one side or on two sides of the fiber bat.